Method of fast imaging of nmr parameters with variably-accelerated sensitivity encoding

Abstract

A method of spatially imaging a nuclear magnetic resonance (NMR)parameter whose measurement requires the acquisition of spatially localized NMR signals in a sample includes placing the sample in an MRI apparatus with a plurality of MRI detectors each having a spatial sensitivity map; and applying MRI sequences adjusted to be sensitive to the NMR parameter. At least one of the MRI sequences is adjusted so as to substantially fully sample an image k-space of the sample. The remainder of the MRI sequences is adjusted to under-sample the image k-space. The method further includes acquiring image k-space NMR signal datasets; estimating a sensitivity map of each of the MRI detectors using a strategy to suppress unfolding artefacts; and applying the estimated sensitivity maps to at least one of the image k-space NMR signal data sets to reconstruct a spatial image of NMR signals that are sensitive to the NMR parameter.

Description

[0001]This application claims priority to U.S. Provisional Application No. 62 / 320,197 filed Apr. 8, 2016, the entire content of which is hereby incorporated by reference.[0002]This invention was made with Government support under grants EB007829, CA166717, EB009731, NS083435, and EB015555, awarded by the National Institutes of Health. The Government has certain rights in the invention.BACKGROUND1. Technical Field[0003]The field of the currently claimed embodiments of this invention relates to imaging of nuclear magnetic resonance (NMR) parameters, and more particularly to imaging of NMR parameters with variably-accelerated sensitivity encoding.2. Discussion of Related Art[0004]There are many parameters that can be measured by NMR and magnetic resonance imaging (MM) including nuclear spin density, longitudinal relaxation time (T1) (1), longitudinal relaxation time in the rotating frame (T1ρ) (2), transverse relaxation time (T2) (1), the inhomogeneously broadened T2 (T2*) relaxation t...

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Problems solved by technology

This often leads to undesirably long overall acquisition times to perform such measurements that can preclude their acquisition in patient studies, especially when the signal-to-noise ratio (SNR) of the parameter measurement is limited, as is often the case.

Although the SLAM method can provide dramatic acceleration factors and substantially higher SNR efficiency than conventional methods (10-13), other than by redefining compartments, it cannot distinguish heterogeneous information inside the compartments and is hence limited in applications where intra-compartmental information is needed down to the original pixel / voxel resolution of the image.

However, application of the SENSE technique to parametric imaging of parameter exhibiting low SNR as compared to the underlying MRI signal being acquired, leads to spatial image ‘unfolding’ artifacts that limit the acceleration factors that can be practically used.

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